404 Foreign and Miscellaneous Intelligence. 



the nitrate of potash always contains some water, and the sulphuric 

 acid is seldom so concentrated as to contain less than 18 J per cent. 

 The acid distils at 266 F., and its specific gravity is between 1.4 and 

 1.395. 28 Ibs. of purified nitre, with 13^ Ibs. of sulphuric acid, of 

 1.85, yielded 34 Ibs. of nitric acid, of 1.30 specific gravity ; and the 

 same quantity of nitre, with 27-jr Ibs. of sulphuric acid, gave 37-J Ibs. 

 of nitric acid, of 1.30*. Besides, the first process required almost 

 twice as much fuel and much more time than the second. 



In conclusion, M. Mitscherlich mentions some remarkable proper- 

 ties of nitric acid, of 1.522 specific gravity. Iron, tin, and several 

 other metals, may be put into, and even boiled in it, without the 

 least effect ; whilst zinc is immediately oxidized and dissolved!. 



35. ON A PECULIAR PROPERTY OF ALLOYS. (By F. Rudberg%.) 



In a course of experiments which I lately made on the specific heat 

 of lead and tin and some of their alloys, I observed a very remarkable 

 proportion attending the specific heat of these alloys, and was parti- 

 cularly struck when, on repeating the experiments on other metals, 

 I found the same proportion also to take place in them ; so that it 

 might, perhaps, be considered as a general property of alloys. 



The following apparatus was used in the experiments : A cubic 

 vessel of thin iron plate, eight inches in height, was placed in ano- 

 ther, of such dimensions that the sicles of the outer were everywhere 

 two inches distant from the inner vessel ; the intermediate space was 

 filled with snow. The larger vessel could be closed with a cover, 

 the lower surface of which was blackened, and the upper covered with 

 snow. In the middle of the central vessel, the inner surface of which 

 was also blackened, there was a very thin cup of tin-plate on a ring 

 of platina, suspended by platina wire from the sides of the inner 

 vessel. A cover of tin-plate was made exactly to fit the opening of 

 the cup, and had a central opening for a cork, through which the 

 tube of a Centigrade thermometer passed ; so that, if the cover was 

 placed on the cup, the bulb of the thermometer was nearly in its 

 middle. The external surface of both the cup and cover were 

 blackened. 



The cup having been put on the ring was filled with the metal, or 

 alloy, whilst in a state of fusion ; the cover, with the thermometer, 

 which had been previously heated, was placed on it, the external 

 cover also put on, and the time which the mass required for cooling, 

 carefully watched. By comparing the different lengths of time which 

 the metal or alloy requires to cool, every ten degrees before and 

 after its becoming solid, with those which mercury requires for the 



* According to Thenard, from 100 parts of nitre and 66 % of sulphuric acid 

 40.8 of very strong nitric acid, and from the same quantity of nitre with 144 parts 

 of sulphuric acid, 81.6 parts of nitric acid of the same strength were obtained. 

 These results appear to M. Mitscherlich to be erroneous. 



f Poggendorff's Annalen. 



J From the Kongl. Svensk. Vetensk. Acad. Handlingar, 1829. 



All the temperatures in this paper are expressed in the Centigrade scale. 



